From 394c476f2aa7bb282bad4f7ebb43d4f29581618d Mon Sep 17 00:00:00 2001
From: henrygd <hank@henrygd.me>
Date: Sun, 30 Nov 2025 14:36:00 -0500
Subject: [PATCH] strip ansi escape sequences from docker logs (#1478)

---
 agent/docker.go      | 12 +++++++++-
 agent/docker_test.go | 57 ++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 68 insertions(+), 1 deletion(-)

diff --git a/agent/docker.go b/agent/docker.go
index 929aed6f..b01e828a 100644
--- a/agent/docker.go
+++ b/agent/docker.go
@@ -14,6 +14,7 @@ import (
 	"net/url"
 	"os"
 	"path"
+	"regexp"
 	"strings"
 	"sync"
 	"time"
@@ -24,6 +25,10 @@ import (
 	"github.com/blang/semver"
 )
 
+// ansiEscapePattern matches ANSI escape sequences (colors, cursor movement, etc.)
+// This includes CSI sequences like \x1b[...m and simple escapes like \x1b[K
+var ansiEscapePattern = regexp.MustCompile(`\x1b\[[0-9;]*[a-zA-Z]|\x1b\][^\x07]*\x07|\x1b[@-Z\\-_]`)
+
 const (
 	// Docker API timeout in milliseconds
 	dockerTimeoutMs = 2100
@@ -692,7 +697,12 @@ func (dm *dockerManager) getLogs(ctx context.Context, containerID string) (strin
 		return "", err
 	}
 
-	return builder.String(), nil
+	// Strip ANSI escape sequences from logs for clean display in web UI
+	logs := builder.String()
+	if strings.Contains(logs, "\x1b") {
+		logs = ansiEscapePattern.ReplaceAllString(logs, "")
+	}
+	return logs, nil
 }
 
 func decodeDockerLogStream(reader io.Reader, builder *strings.Builder) error {
diff --git a/agent/docker_test.go b/agent/docker_test.go
index b07d80c9..e6f9326c 100644
--- a/agent/docker_test.go
+++ b/agent/docker_test.go
@@ -1203,3 +1203,60 @@ func TestShouldExcludeContainer(t *testing.T) {
 		})
 	}
 }
+
+func TestAnsiEscapePattern(t *testing.T) {
+	tests := []struct {
+		name     string
+		input    string
+		expected string
+	}{
+		{
+			name:     "no ANSI codes",
+			input:    "Hello, World!",
+			expected: "Hello, World!",
+		},
+		{
+			name:     "simple color code",
+			input:    "\x1b[34mINFO\x1b[0m client mode",
+			expected: "INFO client mode",
+		},
+		{
+			name:     "multiple color codes",
+			input:    "\x1b[31mERROR\x1b[0m: \x1b[33mWarning\x1b[0m message",
+			expected: "ERROR: Warning message",
+		},
+		{
+			name:     "bold and color",
+			input:    "\x1b[1;32mSUCCESS\x1b[0m",
+			expected: "SUCCESS",
+		},
+		{
+			name:     "cursor movement codes",
+			input:    "Line 1\x1b[KLine 2",
+			expected: "Line 1Line 2",
+		},
+		{
+			name:     "256 color code",
+			input:    "\x1b[38;5;196mRed text\x1b[0m",
+			expected: "Red text",
+		},
+		{
+			name:     "RGB/truecolor code",
+			input:    "\x1b[38;2;255;0;0mRed text\x1b[0m",
+			expected: "Red text",
+		},
+		{
+			name:     "mixed content with newlines",
+			input:    "\x1b[34m2024-01-01 12:00:00\x1b[0m INFO Starting\n\x1b[31m2024-01-01 12:00:01\x1b[0m ERROR Failed",
+			expected: "2024-01-01 12:00:00 INFO Starting\n2024-01-01 12:00:01 ERROR Failed",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			result := ansiEscapePattern.ReplaceAllString(tt.input, "")
+			assert.Equal(t, tt.expected, result)
+		})
+	}
+}
+